The Internet Protocol (IP) is a widely used protocol which nowadays is extensively used for telecommunication, for example for Voice over IP (VoIP). Along with voice data, it is possible to convey via IP other data such as a picture, e.g. in form of a bitmap, and/or text, e.g. in the form of an ASCII file (American Standard Code for Computer Information Interchange). It is thus possible to establish a multimedia session using voice along with text and/or pictures/video data, e.g. in the form of a video conference.
In order to reduce the number of flows of messages/data between participants for example in a conference to increase reliability and efficiency of the conference session, there is need to multiplex multiple media (audio, video and/or other data such as text, tables etc.) on to a single 5 Tuple (IP Address and Ports) with the result of reducing the number of IP transports, i.e. IP addresses and/or IP ports, used during a multimedia session. Therefore, another positive effect of the multiplexing of multiple media is that the total number of used IP transport addresses and/or ports is reduced per session leading to a larger number of multimedia sessions being able to be run simultaneously if the total number of IP transport addresses and/or ports is limited.
In telecommunications and computer networks, multiplexing, also known as muxing, is a method by which digital data streams are combined into one signal over a shared medium. The aim is to share an expensive resource. For example, in telecommunications, several telephone calls may be carried using one wire. Examples for Multiplexing methods include Time division Multiplexing (TDM) and Frequency division Multiplexing (FDM). The multiplexed signal is transmitted over a communication channel, which may be a physical transmission medium. The multiplexing divides the capacity of the high-level communication channel into several low-level logical channels, one for each message signal or data stream to be transferred. A reverse process, known as demultiplexing, can extract the original channels on the receiver side.
A 5-Tuple is made up of source IP address, destination IP address, source port number, destination port number and the protocol in use and is one of the elements that need to be negotiated between two peers before communication can take place. The negotiation between a sending/source entity and a receiving/destination entity of the signalling and payload parameters based on the Internet Protocol needs to be performed in a manner that is both interoperable with existing legacy devices which don't support this multiplexing and new implementations that do. The aim here is to also try to limit the number of SDP (Session Description Protocol) offer/answers exchanges needed to establish media, i.e. a payload path whereon media are transmitted between the source entity and the destination entity. SDP is a format for describing streaming media initialization parameters. The IETF (Internet Engineering Task Force) published the original specification as an IETF Proposed Standard in April 1998, and subsequently published a revised specification as an IETF Proposed Standard as RFC 4566 in July 2006. SDP is intended for describing multimedia communication sessions for the purposes of session announcement, session invitation, and parameter negotiation. SDP does not deliver media itself but is used for negotiation between end points/terminals/communication devices of media type, format, and all associated properties. The set of properties and parameters are often called a session profile.
Possible ways to reduce the number of flows of data/messages/streams between conference participants for efficiency and reliability reasons have been discussed in the IETF, the current approaches being proposed are discussed in the following drafts submitted to the IETF: draft-ietf-mmusic-sdp-bundle-negotiation-03 and draft-ejzak-mmusic-bundle-alternatives-01 which are incorporated herein as an integral part of this application by reference. Both of these approaches describe a mechanism for multiplexing different media using a new SDP grouping mechanism called “BUNDLE”. In SDP, each media is described by what is called an m-line which includes the source port to be used for that media. The approaches describe how a mechanism for grouping these m-lines would work and how the ports are negotiated using the existing m-line. The disadvantage of both of these approaches is that they cannot fully specify the 5-tuple to be used for multiplexing until they have determined that the peer supports the bundling mechanism so these approaches are not sufficiently efficient.